Incident photon-to-current conversion efficiency IPCE

With the D S SCs containing Hibiscus surattensis extract, the best performances were probably obtained because of the large amount of dye adsorbed on Ti02 (lxl cm2 active surface) in comparison with the other extracts from tropical flowers. Incident photon to current conversion efficiency (IPCE) values of 76% were calculated (2 — 590 nm). Jsc was 5.45 mAcm-2, Voc = 392mV, FF — 54%, and efficiency = 1.14%. Also, the stability of the photovoltaic devices was the best in the case of Hibiscus surattensis, even though it needs to be improved to achieve real long-term stability, especially as far as the sealing quality is concerned. 

A very useful parameter for evaluating the performance of a photoelectrolysis cell is the incident photon to current conversion efficiency (IPCE). This is a measure of the effectiveness in converting photons incident on the cell to photocurrent flowing between the working and counter electrodes. IPCE is also called the external quantum efficiency. 

Photovoltaic performance of the DSSC is described as follows Figure 8 shows the external spectral response curve of the photocurrent for nanocrystalline Ti02 solar cells sensitized by N3 and black dyes with the I /If redox mediator, where the incident photon-to-current conversion efficiency (IPCE) is represented as a function of wavelength. IPCE is obtained by the following equation ... 

Finally, we carried out measurements on complete functional devices. We measured the incident photon-to-current conversion efficiency (IPCE) spectra for devices sensitized with AR25 using as electrolyte a solution containing the redox couple iodine/iodide (see Experimental Section). Figure 4 illustrates the IPCE spectra for an AR25/DSSC. 

The incident photon to current conversion efficiency (IPCE) sometimes referred to also as external quantum efficiency (EQE) corresponds to the number of electrons measured as photocurrent in the external circuit divided by the monochromatic photon flux that strikes the cell. The following product expresses this key parameter ... 

Fig. 5 Photocurrent vs potential plot recorded for a ca. 45 pm thick nanoparticulate Ti02 film, immersed in a 0.1 M HCIO4/0.1 M HCOOH solution and irradiated with a 300-nm monochromatic light (700 pW cm ) from the side of the film/solution boundary. On the left axis is represented the corresponding incident photon-to-current conversion efficiency (IPCE). In the insert is represented schematically (marked in grey ) the illuminated part of the Ti02 film where the electron injection takes place. (Reproduced with permission from [12])...

The incident photon-to-current conversion efficiency (IPCE). 

Successive cycles of thiophene terminal bromination and Suzuki-type coupling reactions with 3-hexylthiophene-2-boronic ester gave intermediate ter- and quaterthiophenes. Formylation of these intermediates and final condensation with cyanoacetic acid in basic medium afforded corresponding oligothiophenes in 70-90% yields. UV-Vis absorption spectra of 2.82 (n = 1, 2) showed maxima at 463 and 473 nm, respectively. Fabrication of DSSCs based on 2.82 (n = 1, 2) showed a high incident photon-to-current conversion efficiency (IPCE) of 70 % in the range 400-650 nm and good maximum power conversion efficiencies of 7.7 and 5.6% under AM 1.5 illumination. 

The N3 and N719 dyes (Table 38.1) show the highest incident photon-to-current conversion efficiency (IPCE) as compared with other dyes. When the optical properties of the dyes are taking into consideration, there are two quantum efficiencies (QEs), that is, an external quantum efficiency (EQE) and an internal quantum efficiency (IQE) [43]. EQE includes the effect of optical losses by transmission and reflection, while IQE refers to the efficiency of the photons that are not reflected or transmitted out of the cell [43]. From the reflection and transmission of a solar cell, the EQE curve can be corrected to obtain the internal quantum efficiency curve [43]. IPCE is related to EQE and therefore IPCE depends on the absorption of light as well as the collection of charges. 

The short circuit photocurrent, Jsc, is defined as integral over the solar spectrum of the monochromatic incident photon to current conversion efficiency (IPCE) of the solar cell under short circuit cmiditions ... 

If the carrier collection efficiency is very good, then the photocurrent, y ph, is determined by the light absorption and charge injection features that are measured by Incident Photon to Current conversion Efficiency (IPCE), also known as the External Quantum Efficiency (EQE) [18]. Examples of the absorption spectra of efficient dyes are shown in Fig. 3 [19], and the corresponding IPCE is shown in the figure together with the final photovoltaic performance. In this type of highly efficient DSC, the measured current can indeed be viewed as completely decoupled from recombination, as in the model of (19). The convolution of IPCE with the solar spectrum describes very well the actual value of /ph. However, in cells with low collection efficiency, one should be careful to calculate correctly the collection... 

External quantum efficiency (EQE) is the ratio of the number of charge carriers produced by the cell to the number of photons incident on the cell (Lianos, 2011). Incident photon to current conversion efficiency (IPCE) (Antoniadou et al, 2010 BriUet et al, 2010 Tode et al, 2010 Varghese and Grimes, 2008 Yu ef a/., 2010), is one way to express EQE, which is defined as ... 

Fig. 10.10 Incident photon to current conversion efficiency (IPCE) measured as a function of photons on a Au/Ti02 diode after heating at 433 K to obtain Au island structures. The inset depicts the formation of the metalhc nanoscale domains. (Reprinted with permission from ref. [65].

As can be seen from Fig. 10a, the incident photon to current conversion efficiency (IPCE) is much higher for the nanotube layer than for the nanoparticle layer of the same thickness, although the particles have a 3 times higher surface area than the tube layers (120 and 29.8 m g , respectively). The higher IPCE can be ascribed to a faster transport time in the... 

P = External Quantum Efficiency (EQE) = Incident Photon-to-current Conversion Efficiency (IPCE). 

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